1. Field of the Invention
The present invention relates to a printing paper which is based on neutralized paper and exhibits excellent performance as toner-transfer paper for electrophotographic printing, and also relates to a method of image formation by electrophotographic printing by use of this printing paper.
The present invention further relates to a printing paper which is based on neutralized paper and is capable of forming sharp images in ink-jet recording, and also relates to a method of image formation by ink-jet printing by use of this printing paper.
2. Related Background Art
An electrophotographic copying machine is exemplified by a copying machine which conducts printing through the process of: charging a photoconductive photosensitive member by means of a temporary electric charger; exposing the photosensitive member to light to form a latent image; developing the latent image with a developing toner of the one- or two-component type, transferring the toner image from the photosensitive member to a printing paper sheet fed from the outside by means of a toner-transfer electric charger, and fixing the transferred toner on the printing paper sheet by action of heat and/or pressure by means of a fixing roller or the like to obtain a final copied image.
The properties required for the transfer paper for such a copying machine are as follows:
(1) optimum surface electrical resistance and optimum surface smoothness and good toner transfer property,
(2) excellent in toner-fixing properties,
(3) less paper dust formation, i.e., causing no image defect due to of the formed paper dust sticking to a photosensitive member, an electric charging roller, etc.,
(4) the formed dust (filler, etc.) does not scrape or abrade the photosensitive member, the paper-delivering roller, fixing rolls, etc.,
(5) generating no curling by action of heat,
(6) generating no variation of the paper dimension by humidity change,
(7) low stiffness, and optimum surface friction coefficient and excellent deliverability.
In recent years, neutralized paper has come to be used widely in place of conventional acidic paper for storability of the paper and other reasons. Japanese Patent Application Laid-open No. 59-191068 discloses toner-transfer paper suitable for electrophotographic printing.
On the other hand, the ink-jet printing system is attracting attention because of ease of high speed printing, color printing, and high-density printing, and therefore the ink-jet printing apparatus has come to be widely used. In particular, for mono-color printing and business color printing, ink-jet printing is required to be suitable for printing on inexpensive ordinary paper which is available in offices, not on paper exclusively for use in ink-jet printing.
No toner-transfer paper is presently known which is suitable also for ink-jet printing.
When the toner-transfer paper, which is neutralized paper, is used for ink-jet printing, disadvantages are involved such as insufficient ink-fixing properties, insufficient water fastness of the printed image owing to water-soluble printing agent, and insufficient coloring ability of the coloring agent.